Answer:
68% of these phones last 3.87 years.
Step-by-step explanation:
Exponential distribution:
The exponential probability distribution, with mean m, is described by the following equation:
In which is the decay parameter.
The probability that x is lower or equal to a is given by:
Which has the following solution:
The probability of finding a value higher than x is:
The average lifetime of a certain new cell phone is 3.4 years.
This means that
So
68% of these phones last how long (in years)?
This is x for which:
Then
68% of these phones last 3.87 years.